Yes they pay me (implicitly) as I work in a project led by them. But again, they are the first to update their CV and make a noise. Hiring someone just to publish is not right. I know for a fact that they even don't understand most part of the manuscript.

Hiring you to publish is not right?! OP, have you read the grant proposal that was used to obtain your funding? Can you do this work without the funding?

Yes, I can do. I used a public data set. I started developing this paper way before I joined them. Their argument is that since I used their project time (paid from their project) I should include them as co-authors...kind of tit for tat.

Names come from academic contribution, not from providing money. Or should we also include the director (or someone else) from the funding institution? If they fire you for this, I think you have a case for illegal firing, or at least the publicity of such a case would disgrace them academically, even if they case is not legally sound. Especially if you started the project before starting to work there.

Names come from academic contribution, not from providing money. Or should we also include the director (or someone else) from the funding institution? If they fire you for this, I think you have a case for illegal firing, or at least the publicity of such a case would disgrace them academically, even if they case is not legally sound. Especially if you started the project before starting to work there.

I have experienced this issue from both perspectives (post doc and grant-holder). You need to be absolutely honest with yourself - if the research question is yours, the method yours, the analysis, interpretation, and write up done by you, then they have no legitimate claim to co-authorship. But bear in mind that there is a tendency to under-estimate the extent to which grant-holders defined the research question and set out the research design. If they had no role in this, then what exactly is the relation of your work to the funded grant? Be realistic.

The second issue is that *assuming* they in fact have no legitimate claim to co-authorship, if you start a conflict over this, you are most likely dead on the job market. Add their names to the papers that they know about, start looking for a new job, and hold as much back as possible for your pipeline.

I have experienced this issue from both perspectives (post doc and grant-holder). You need to be absolutely honest with yourself - if the research question is yours, the method yours, the analysis, interpretation, and write up done by you, then they have no legitimate claim to co-authorship. But bear in mind that there is a tendency to under-estimate the extent to which grant-holders defined the research question and set out the research design. If they had no role in this, then what exactly is the relation of your work to the funded grant? Be realistic.
The second issue is that *assuming* they in fact have no legitimate claim to co-authorship, if you start a conflict over this, you are most likely dead on the job market. Add their names to the papers that they know about, start looking for a new job, and hold as much back as possible for your pipeline.